Processes for alkylating a variety of alkylatable aromatic compounds by contacting such aromatic compounds with a hydrocarbon radical providing source such as an olefin or alcohol are widely known. Typically, alkylatable aromatic compounds are mononuclear aromatic compounds, including those substituted with a hydroxyl, amine or an ether group. The alkylation has been carried out in the presence of homogeneous and heterogeneous catalyst systems.
Ring alkylated aromatic amines have been some of the products produced by alkylation procedures. Ring alkylated aromatic amines have a variety of uses in chemical synthesis. Some of the early uses were intermediates for substituted isocyanates, herbicidal compositions, dyestuffs and textile auxiliary agents. More recently aromatic amines have been utilized as chain lengthening components in polyurethane systems. These are commonly referred to as chain extenders.
Representative references which illustrate some of the early processes in forming ring alkylated aromatic amines are as follows.
British Patent No. 414,574 discloses the reaction of aniline with various olefins, e.g., cyclohexene and alcohols, e.g., butanol in the presence of a neutral or weakly acidic catalyst system commonly referred to as hydrosilicates at temperatures from 200.degree.-270.degree. C. Ortho and para-cyclohexylaniline, N-cyclohexylaniline, N-butylaniline and para-methyl-ortho-cyclohexylaniline and N-cyclohexyl-para-toluidine are listed as representative products.
British Patent No. 846,226 discloses ring alkylation of aromatic amines with olefins using active, substantially neutral bleaching earths of the montmorillonite type as a catalyst.
West Germans No. AS 1,051,271 discloses the ring alkylation of aniline with an olefin, e.g., ethylene, in the presence of kaolin or in the presence of aluminum and aluminum alloys. Alkylation with higher olefins, e.g., propylene, butylene, etc., was carried out in the presence of Friedel-Crafts catalysts or bleaching earths under liquid phase conditions at temperatures from 150.degree.-350.degree. C. Examples of catalytic systems included aluminum chloride, zinc chloride, boron trifluoride, sulfuric acid, phosphoric acid and bleaching earth. Ring alkylation at the ortho-position was predominant, although other products such as the di-and tri-alkylated aniline product were produced.
In an article by Zollner and Marton, Acta Chim. Hung. Tomus 20. 1959 (Pages 321-329), the vapor phase alkylation of aniline with ethanol was effected in the presence of aluminum oxide.
U.S. Pat. Nos. 3,649,693 and 3,923,892 discloses the preparation of ring alkylated aromatic amines by reacting an aromatic amine with an olefin in the presence of aluminum anilide, optionally including a Friedel-Crafts promoter. Reaction products include 2-ethylaniline, and 2,6-diethylaniline.
Stroh, et al., in U.S. Pat. Nos. 3,275,690; 2,762,845, Japanese Sho No. 56-110652, and, as mentioned previously, West German No. AS 1,051,271, disclose various processes for preparing alkylated aromatic amines by reacting an aromatic amine with an olefin in the presence of Friedel-Crafts catalysts as well as a combination of the Friedel-Crafts catalysts in the presence of halogen compounds combined with aluminum. Representative reaction products included 2-cyclohexylaniline, diethyltoluenediamine, diethylaniline, diisopropylaniline and mono-tert-butylaniline.
The art, e.g., Netherlands Application No. 6,407,636, has recognized that alkylation of various aromatic and heterocyclic compounds can be carried out in the presence of a zeolite having a pore size from 6-15 Angstroms wherein active cation sites are obtained with an exchangeable metal or hydrogen cations in their ordered internal structure. Alkylating agents include olefins having from 2 to 12 carbon atoms, alkyl halides such as propylbromide and ethylchloride; and alkanols, such as, methanol, ethanol, and propanol. Various compounds were suggested as being suited for alkylation and these include both the heterocyclic and aromatic ring compounds. For aromatic amine alkylation it was suggested that a zeolite with a disperse distribution of acidic sites should be utilized. It was believed the highly acidic zeolite catalysts, which have a high density of acidic sites, may bind the amine to the catalyst and block the pore structures. In Example 1, aniline was alkylated with propylene using sodium zeolite X having a pore size of 13 Angstroms; numerous alkylated amines were produced. Example 3 shows alkylation of diphenylamine with cyclohexene using a rare earth exchanged 13 X zeolite. Again, numerous ring alkylated products were produced and high temperatures, e.g. 300.degree. C. and above, apparently were required to weaken the amine-acid bond.
French Patent No. 1,406,739, which is equivalent to Netherlands Application No. 6,407,636, discloses the preparation of alkylated aromatic compounds having polar substitutions thereon utilizing alumino-silicates having a pore size of at least 6 Angstroms as a catalyst. Cations of low valence were deemed to have been particularly effective for the ring alkylation of aromatic compounds having weakly basic substituents such as aromatic amines. The examples show the alkylation of aniline with propylene in the presence of a sodium zeolite X and alkylation of diphenylamine with propylene in the presence of a 13X molecular sieve which has undergone a partial exchange with rare earth metals and having a pore size of 13A.degree..
The following patents show the use of dealuminated or high silica zeolites for a variety of hydrocarbon conversion processes. The patents are as follows.
U.S. Pat. No. 3,506,400 discloses the preparation of crystalline alumino silicates having high silica to alumina mole ratios by heat treatment of the zeolite in the presence of water to effectuate removal of a substantial portion of alumina from the zeolite structure. These zeolites, which contained a higher silica to alumina ratio, were shown to be effective for catalytic cracking.
U.S. Pat. No. 3,761,396 discloses the conversion of hydrocarbons in the presence of a dealuminated zeolite, the dealumination being accomplished by extracting framework aluminum from the crystalline molecular sieve using acetylacetone as the extracting agent. The examples show the use of partially dealuminated zeolites as being effective catalysts for the alkylation of benzene with propylene.
U.S. Pat. No. 3,937,791 discloses various hydrocarbon conversion processes using a dealuminated zeolite having framework aluminum extracted therefrom. Some of the early techniques for dealumination involved treatment with acid or chelating agents such as ethylenediamine tetraacetic acid (EDTA); however, it was preferred that chromium chloride be used as the free agent for removing framework aluminum because it leaves a material which is more porous than obtained with EDTA.
U.S. Pat. No. 3,493,519 discloses a hydrothermally stable catalyst system for hydrocarbon conversion. The catalyst is prepared by calcining an ammonium Y crystalline alumino-silicate in the presence of a rapidly-flowing steam and base exchange the steam product with an ammonium salt and then treating the exchange product with a chelating agent for extracting framework aluminum. The catalyst was suggested as being suited for alkylation, dealkylation, isomerization, disproportionation, translkylation and other types of hydrocarbon conversion.
U.S. Pat. Nos. 3,178,365; 3,281,483; 4,259,537; 4,395,372 and 4,393,262 disclose the alkylation of aromatic hydrocarbon compounds with an olefin in the presence of various crystalline alumino-silicates, such as crystalline alumino-silicates having undergone previous transformation by reaction with a nitrogen oxide containing compound, a hydrogen mordenite, a ZSM catalyst exchanged with a VIa metal; crystalline alumino-silicates promoted with sulfur dioxide and dealuminated zeolites. The dealuminated and high silica zeolites (ZSM) are disclosed as having particular activity for the alkylation of benzene.
Although the prior art has disclosed that a variety of catalytic systems can be utilized in the alkylation of aromatic hydrocarbons and aromatic amines, the art also teaches that a variety of reaction products are produced, including both ortho and para-isomers of mononuclear aromatic amines as well as, mono, di and tri alkyl substituted amines. In addition, the prior art teaches that neutral to weakly acidic catalysts are preferred for effecting ring alkylation of the aromatic amines. Even though the prior art has suggested preferred catalytic systems such systems also involve batch, liquid phase operation which may be difficult to operate over an extended period of time, and tend to give more para product. In addition, many of the processes suffer from poor conversion, poor reaction rate and an inability to produce high ortho to para isomer ratios at high conversion.